There are 2 similar blocks of code in sun.awt.X11GraphicsEnvironment#initDevices

            devices.put(id, old.containsKey(id) ? old.remove(id) :
                                                  new X11GraphicsDevice(id));

and in sun.awt.CGraphicsEnvironment#initDevices:

            devices.put(id, old.containsKey(id) ? old.remove(id)
                                                : new CGraphicsDevice(id));

We can avoid redundant Map.containsKey calls. Instead of separate containsKey call we can call old.remove and then compare result with null.